U.S. Secretary of State Hillary Clinton says Syrian President Bashar al-Assad can demonstrate the seriousness with which he has accepted a U.N. peace plan by withdrawing troops from civilian areas of Syria. President Assad on Tuesday agreed to the plan brokered by former U.N. Secretary-General Kofi Annan.

Secretary Clinton says President Assad's acceptance of the plan is an important first step toward ending Syria's year-long uprising. But Clinton says she wants more than promises.“Given Assad's history of over-promising and under-delivering, that commitment must now be matched by immediate actions," she said.

Clinton says the international community will judge President Assad's sincerity and seriousness by what he does, not by what he says. “If he is ready to bring this dark chapter in Syria's history to a close, he can prove it by immediately ordering regime forces to stop firing and begin withdrawing from populated areas. He can also allow international aid workers unfettered access to those in need," she said.

Clinton says Damascus should also free political prisoners, permit peaceful political activity, allow unobstructed access for news media and begin a political process that leads to a democratic transition. If President Assad takes these steps, she says U.N. and Arab League envoy Kofi Annan will work with the opposition to take steps of their own.

“So that the bloodshed ends, that there won't be violence coming from opposition forces, that humanitarian aid will be permitted to come into areas that the opposition has been holding," she said.

The six-point Annan plan calls for a U.N.-monitored ceasefire, access for humanitarian aid workers and an inclusive, Syrian-led political transition to a democratic, multi-party political system.

Middle East analyst Steve Heydemann with the United States Institute of Peace says the plan is constrained by its foundation on a U.N. resolution that was stripped of demands for President Assad to step down so as to avoid a Russian and Chinese veto. “They really don't go very far. They talk about very general kinds of commitments to dialogue. They talk about very general commitments to things like pulling forces out of urban areas. But we've seen the Assad regime agree to these sorts of things in the past and fail to implement them," he said.

Heydemann says he has modest expectations about what Mr. Annan can do. “What we are seeing is a consistent pattern on the part of the Assad regime of agreeing to these international frameworks, in particular because I think they do support the efforts of their protectors, the Russians and the Chinese, but very little changes as a result. And my sense is that we are likely to see a repeat of that in this case," he said.

Recognizing the challenges, Mr. Annan says the plan's implementation will be key to ending the fighting and moving toward democratic governance in Syria.

The British-based Syrian Observatory for Human Rights says at least 10 people were killed Tuesday as government forces fired at civilians and battled rebels in several parts of the country, including the northwestern province of Idlib, the Damascus suburbs and the central city of Homs.